Biological samples, such as tissue or cellular extracts or lysates, enzymes, proteins, peptides, nucleic acids, fatty acids, glycerides, carbohydrates, oligosaccharides and saccharides, are commonly prepared at a first site, stored in a container, and transported to a second site for processing. One example of this is in diagnostic devices and/or in DNA/RNA amplification processes. This may require that the biological sample, which may be an enzyme such as a polymerase or reverse transcriptase, is stored for significant periods of time in the container and/or subject to vibrations and/or other external forces during transportation.
A convenient way of supplying such biological samples is to freeze-dry the biological sample in the container prior to transportation. The container is typically a tube of cylindrical cross-section having a single internal chamber. The freeze-drying process typically involves freezing a liquid sample, reducing the ambient pressure, and then gradually adding enough heat to allow sublimation of the water contained within the frozen liquid. The result is a coagulated, dehydrated sample formed at the bottom of the container; the container is then sealed and the biological sample (which may contain an enzyme) is stored, and transported, in this freeze-dried state.
When the biological sample is subsequently required for processing, it can be reconstituted by adding water to the freeze-dried material. The amount of biological sample dissolved for a given volume of water added can be critical; for example, if the amount of biological sample dissolved is too small, the strength of the solution may be insufficient.
However, it has been observed that when the freeze-dried material is supplied in existing tubes, some of the freeze-dried material remains un-dissolved when water is subsequently added. This can result in a solution of insufficient strength, as mentioned above.
Furthermore, biological samples freeze-dried, stored and transported in this way are often of high value; accordingly, un-dissolved biological sample is wasteful and can increase costs.
It is an object of the present invention to at least mitigate some of the problems of the prior art.